The two F-15s were flying with the plane east of Florida, and a NORAD spokesman said the windows appeared frosted. Though the jets did not enter Cuban airspace, NORAD has kept in touch with Cuban authorities through the U.S. Coast Guard. Both NORAD and the F.A.A. are still tracking the plane.

Hypoxia is speculated to be the cause of the unresponsiveness, as a loss of oxygen could lead to all passengers and crew becoming unconscious.

The plane is a Socata TBM-700 light business and utility aircraft that had departed from Rochester, New York, for Naples, Flo., with a landing time set for around 2:05 p.m. It is unclear how much fuel is left.

A similar situation occurred just last week, when an unconscious pilot flew a small plane into restricted airspace over Washington, D.C. NORAD also sent fighter jets to escort the plane, until it eventually crashed into the Atlantic Ocean.